Small cylindrical stub antenna with loading capacitance



J. HEINS Dec. 12, 1967 SMALL CYLINDRICAL STUB WITH LOADING CAPACITANCE Filed Aug. 13, 1964 United States Patent C 3,358,286 SMALL CYLINDRICAL STUB ANTENNA WITH LOADING CAPACITAN CE John Lewis Heins, Massapequa Park, N.Y., assiguor to Eggud Electronics, Inc., Massapequa Park, N.Y., a co1'- poration of New York Filed Aug. 13, 1964, Ser. No. 389,293 3 Claims. (Cl. 343-750) ABSTRACT OF THE DISCLOSURE An antenna system of a length .003 to .1 Wavelength and having an outer conducting structure electrically and mechanically connected to an inner conductor at one end of the structure with the opposite end of the inner conductor coupled to ground through a variable reactance.

This invention relates to an antenna system having a radiating element physically and electrically small in length in relation to its operating Wavelength or longest operating wavelength. Which system consists of a radiating element and a means of top loading that eliminates the need for the well known large top structure to provide capacity loading. (Physically and electrically small in length for the purpose of this invention is delined as a length of from .O03 to .1 of the operating Wavelength. Top loading deiines the capacity or capacity and inductance introduced at the top of an antenna to reduce the magnitude of the capacitive reactance appearing in the base 14 impedance.)

Referring to the drawing the antenna system consists of a metallic tube 15 insulated from ground with a length of from .003 to .1 of the lowest wavelength at which it is desired to operate, a center conductor 17, connected at one end to the metallic tube 16 supported on insulating spacers and connected to a lixed or variable capacitor 18 or combination of inductance 20 and capacitor 18 at the other end connected to a transmitter and/ or receiver and ground. When the tube which is the radiating element is installed vertically the far electric iield radiated by the antenna is vertically polarized.

The principal feature of this invention is a method of top loading at the bottom a radiating element electrically and physically small in relation to its operating wavelength -by means of a simple capacitor or capacitor and inductance without having to resort to top loading or loading methods Well known which either appreciably increase antenna size or which load at the expense of increased complication and reduced eiciency.

Another object of this invention is to provide an antenna system having a radiating element physically and electrically small in relation to its operating Wavelength which because of the method of top loading described in this invention has a higher radiation eiiciency than other antennas of similar length now in use. Specifically the radiation of more than 1% ,of the input power to the antenna.

Another object of this invention is to provide an antenna system whose base impedance remains relatively constant under conditions Where a moving metallic or other type object is introduced into its near field.

Another object of this invention is a simple method Vof varying the antenna loading with operating frequency to maintain optimum radiation efiiciency.

Another object of this invention is to provide an antenna physically and electrically small in relation to its operating wavelength which is dimensionably suitable for installation on aerospace vehicles yand which when so in- ICC stalled, will, in conjunction with suitable transmitting and receiving apparatus meet the communications requirements of the aerospace vehicles environment.

Another object is to provide a physically and electrically small antenna system which can be turned over a Wide range of frequencies and maintain its eiciency.

Also an object of this invention is to provide an antenna system physically and electrically small in relation to its operating wavelength for non-aerospace applications which has better operating etiiciencies than structures employing classical loading schemes.

An important feature of this invention is that the antenna system has adequate bandwidth characteristics for communication and data transmission purposes and in all cases greater than 1.7% of the lowest operating frequency.

FIG. l illustrates a lirst embodiment of the invention.

FIG. 2 illustrates a second embodiment of the invention eliminating the coupler of FIG. 1 and adding the loading coil.

FIG. 3 illustrates a third embodiment of the invention utilizing both the coupler and the loading coil addition.

FIG. 4 illustrates still a further embodiment of the invention including a resistance matching transformer.

Referring to the drawing, FIG. 1 illustrates an antenna system in -association with a source of radio frequency energy such as any well known radio transmitter and a radio receiver both operating on the proper wavelengths. (As is well known the operation of an antenna is reciprocal therefore radiation and reception are synonymous for the purpose of this description.)

Radio frequency energy is fed from 11 by a radio frequency transmission line or direct connection 12 t0 13 which is a Well known antenna coupling device which tunes out the reactive component of the antenna impedance and matches its resistive component to the transmission line 12. These components appear at 14. The radio frequency energy is then fed into the radiating element 15 at point 14. At 16 the outer shell of the radiator is connected to the inner conductor which in turn is connected to the loading capacitor 18. 18 is adjusted for the value that provides maximum radiation eiiiciency from the radiating element.

FIG. 2 shows an antenna system with the elimination of the coupler 13 of rectangle 10. Operation is identical with the exception that inductance 20 and capacitor 18 can be adjusted to provide loading for optimum radiation eiiciency and `direct matching to the transmission line 12 at 14. This direct matching is only possible at certain discrete frequencies.

FIG. 3 illustrates an antenna system utilizing both the coupler 13 and the capacitor inductor 18, 20 loading.

These units 13, 20, and 18 are adjusted for maximum radiation eliiciency.

FIG. 4 shows an -antenna system using only a well known resistance matching transformer or capacitor matching device 23. Inductance 20 and capacitor 18 are adjusted to make the input impedance at 14 a resistance. 23 is required because depending on wavelength this resistance will be different from the impedance of the transmission line or direct connection.

In rectangles 10, 19, 21, and 22 capacitor 18 and the combination of capacitor inductor 18, 20, can also be adjusted to further reduce the changes of antenna impedance at the base 14 caused by objects placed in the near field of the antenna.

I claim:

1. An antenna system comprising; a hollow metal openended tube having a length from .003 to .1 of the operating wavelength; a center conductor within said tube electrically and mechanically connected thereto at `the top; and a loading capacitive reactance coupled between Y the bottom of said center conductor and ground.

2. The antenna system claimed in claim 1 wherein said react-ance is variable.

3. The antenna system claimed in claim -1 wherein ,said tube is cylindrical.

4 References Cited UNITED STATES PATENTS 2,463,547 3/ 1949 Meier 343-83 1 X 5 2,529,213 1.1/ 1950 Goldsmith 343-831 X 3,151,327 9/1964 Levy et al 343-705 ELI LIEBERMAN, Primary Examiner. 

1. AN ANTENNA SYSTEM COMPRISING; A HOLLOW METAL OPENENDED TUBE HAVING A LENGTH FROM .003 TO .1 OF THE OPERATING WAVELENGTH; A CENTER CONDUCTOR WITHIN SAID TUBE ELECTRICALLY AND MECHANICALLY CONNECTED THERETO AT THE TOP; AND A LOADING CAPACITIVE REACTANCE COUPLED BETWEEN THE BOTTOM OF SAID CENTER CONDUCTOR AND GROUND. 